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# This program is copyright 2011 Percona Inc.
# Feedback and improvements are welcome.
#
# THIS PROGRAM IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED
# WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
# MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
#
# This program is free software; you can redistribute it and/or modify it under
# the terms of the GNU General Public License as published by the Free Software
# Foundation, version 2; OR the Perl Artistic License. On UNIX and similar
# systems, you can issue `man perlgpl' or `man perlartistic' to read these
# licenses.
#
# You should have received a copy of the GNU General Public License along with
# this program; if not, write to the Free Software Foundation, Inc., 59 Temple
# Place, Suite 330, Boston, MA 02111-1307 USA.
# ###########################################################################
# WeightedAvgRate package
# ###########################################################################
{
# Package: WeightedAvgRate
# WeightedAvgRate calculates and returns a weighted average rate.
package WeightedAvgRate;
use strict;
use warnings FATAL => 'all';
use English qw(-no_match_vars);
use constant PTDEBUG => $ENV{PTDEBUG} || 0;
# Sub: new
#
# Required Arguments:
# target_t - Target time for t in <update()>
#
# Optional Arguments:
# weight - Weight of previous n/t values (default 0.75).
#
# Returns:
# WeightedAvgRate
sub new {
my ( $class, %args ) = @_;
my @required_args = qw(target_t);
foreach my $arg ( @required_args ) {
die "I need a $arg argument" unless defined $args{$arg};
}
my $self = {
%args,
avg_n => 0,
avg_t => 0,
weight => $args{weight} || 0.75,
};
return bless $self, $class;
}
# Sub: update
# Update weighted average rate. Param n is generic; it's how many of
# whatever the caller is doing (rows, checksums, etc.). Param s is how
# long this n took, in seconds (hi-res or not).
#
# Parameters:
# n - Number of operations (rows, etc.)
# t - Amount of time in seconds that n took
#
# Returns:
# n adjust to meet target_t based on weighted decaying avg rate
sub update {
my ($self, $n, $t) = @_;
PTDEBUG && _d('Master op time:', $n, 'n /', $t, 's');
if ( $self->{avg_n} && $self->{avg_t} ) {
$self->{avg_n} = ($self->{avg_n} * $self->{weight}) + $n;
$self->{avg_t} = ($self->{avg_t} * $self->{weight}) + $t;
$self->{avg_rate} = $self->{avg_n} / $self->{avg_t};
PTDEBUG && _d('Weighted avg rate:', $self->{avg_rate}, 'n/s');
}
else {
$self->{avg_n} = $n;
$self->{avg_t} = $t;
$self->{avg_rate} = $self->{avg_n} / $self->{avg_t};
PTDEBUG && _d('Initial avg rate:', $self->{avg_rate}, 'n/s');
}
my $new_n = int($self->{avg_rate} * $self->{target_t});
PTDEBUG && _d('Adjust n to', $new_n);
return $new_n;
}
sub _d {
my ($package, undef, $line) = caller 0;
@_ = map { (my $temp = $_) =~ s/\n/\n# /g; $temp; }
map { defined $_ ? $_ : 'undef' }
@_;
print STDERR "# $package:$line $PID ", join(' ', @_), "\n";
}
1;
}
# ###########################################################################
# End WeightedAvgRate package
# ###########################################################################
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